Transgenic and Genome Editing Facility Shared Resource (TGEF-SR) Project Summary The ability to introduce foreign genes into the germ line, to selectively ablate endogenous genes, or to genetically edit specific genes in the mouse and rat genome, has proven to be one of the most powerful experimental tools available for understanding specific genetic requirements for tumor promoting regulatory pathways. In the area of oncology, genetically engineered mouse models have revealed the molecular pathways by which proto-oncogenes predispose cells to develop malignant tumors or how tumor suppressor genes maintain normal growth control. Transgenic strategies have also revolutionized the way we approach the complex problems associated with carcinogenesis, including the development of novel therapeutic intervention strategies. To support cancer research and utilization of this powerful technology, the Purdue University Center for Cancer Research (PCCR) Transgenic and Genome Editing Facility Shared Resource (TGEF-SR) was established in 1998. The PCCR's TGEF-SR is a state-of-the-art facility that offers a large number of services to the Center membership, including the creation of transgenic, knock-out, and gene-edited mouse and rat models that can assist in dissecting transcriptional, signaling, and environmental influences on tumor initiation, progression and metastasis. Additionally, these models have been instrumental in dissecting the importance of immune cells and stromal infiltrates to tumor progression, and have helped to identify novel cancer stem cell lineages that are often resistant to conventional chemotherapeutics. The TGEF-SR provides a wide range of services to the PCCR community that can be divided into 2 main categories, genome editing and assisted reproduction. The Resource offers several options for gene editing, including: (i) traditional transgenic technology to produce animals with exogenous gene sequences randomly inserted into the genome; (ii) CRISPR-mediated knock-outs to delete small or large, targeted pieces of DNA, resulting in gene disruption or inactivation; (iii) CRISPR-mediated, targeted, homology-directed knock-ins of DNA sequences to produce subtle changes in gene sequence; (iv) insertion of large cassettes or entire gene replacements; and (v) traditional knock-outs produced by injection of gene-targeted ES cells into blastocysts. The last few years has seen a major shift towards CRISPR-mediated projects, with 31 CRISPR/cas9 projects, in both rats and mice, completed in a 3-year period. In support of genetically engineered rodent colonies, the TGEF-SR also offers services to assist with the maintenance of mouse colonies and to overcome difficulties associated with breeding challenging lines, including re-derivation by embryo transfer to import new lines from outside facilities, embryo and sperm cryopreservation to preserve the valuable gene-edited lines generated, and in vitro fertilization to overcome breeding problems or allow rapid expansion of a line. The TGEF-SR is poised to continue offering excellent services to rapidly move cancer models towards effective patient care.